1. Field of the Invention
The present invention relates to a car-mounted electronic control device, in particular, to improvements in a starting control for measuring a target awakening time so as to prevent a preheat control of cooling water or a detection of evaporation of a fuel from being left for a long time, and more particularly, to a car-mounted electronic control device capable of making a start control with a low power consumption, in a high precision and at a low cost.
2. Description of the Related Art
In the related art, there is well known a car-mounted electronic control device which comprises: a main control circuit unit including a microprocessor to become a main CPU powered by a car-mounted battery through a switching element responding to the action of a power source switch and a main power source circuit, for driving various electric loads in response to the action states of various input sensors and the contents of a first program memory; and a timer circuit unit powered at all times by the car-mounted battery through an auxiliary power source circuit, for measuring the lapse time after the engine was stopped, so that it may generate starting output signals, when the measured time reaches a predetermined target measurement time, to connect the main power source circuit with the car-mounted battery.
According to Patent Document 1, Japanese Patent Publication JA-A-2003-315474 “Electronic Control Device and Semiconductor Integrated Circuit”, for example, the concept of a soak timer of a wide variety of specifications for measuring the left time at a measurement time and a measurement precision according to applications have been presented on the soak timer for detecting the left time on the preheat control of cooling water or the detection of evaporation of a fuel.
According to Patent Document 2, Japanese Patent Publication JP-A-11-338572 “Clock Generator”, moreover, there has also been presented the concept of using a ring oscillator as a high-speed oscillator in a mobile telephone having a low-speed oscillator to be used in a low power consumption mode and the high-speed oscillator to be used in an ordinary operation mode. In addition, the concept of cumulatively correcting the oscillation frequency of the ring oscillator comparing the oscillation frequency of the low-speed oscillator, as well as the operation principle of the ring oscillator have also been described in Patent Document 2.
(1) Description of Problems of the Related Art
The electronic control device according to Patent Document 1 is provided with a highly precise external oscillator, and a reference clock is generated on the basis of the oscillatory signal of the oscillator. The left time is measured by counting the reference clock signal. The external oscillator, however, increases the power consumption and the number of parts, causing the electronic control device to be a high price.
On the other hand, the electronic control device according to Patent Document 2 needs a highly precise oscillator as the low-speed oscillator, and the oscillation frequency itself of the high-speed oscillator must be adjusted. Therefore, the clock generator causes a complicate and expensive construction just for a timing application.